Antenna system



Nov. 1, 1938. v LANDON .7 2,135,037

ANTENNA SYSTEM Filed Oct 51, 1936 RECEIVE)? END.

ISNUBMOI? Vernon D. Landon Patented Nov. 1, 1938 PATENT OFFICE ANTENNA SYSTEM Vernon D. Landon, Haddonfield, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application October 31, 1936, Serial No. 103,508

'6 Claims. (01. 250-20) My invention relates to radio, antenna systems and more particularly to a receiving antenna which is responsive throughout a range of frequencies, and which includes means for reducing the pick-up of noise-producing impulses.

It has been found that noise impulses are picked up in the receiving antenna lead-in. I am aware of the use of shielded or transposed lead-ins which reduce the noise impulse pick-up. Gen- 10 erally, the use of shielded or transposed lead-ins will not entirely eliminate noise impulses from such leads. The residual pick-up in shielded leads is partly due to imperfect symmetry and partly to imperfect shielding. Also, some noise may be 55 picked up on the antenna itself. 7 p

The present invention contemplates an im.

provement in shielded or transposed transmission lines which enables the user to maintain a substantially perfect balance between the conductors of the line and ground.

Another object is to provide a means for unbalancing the transmission line so that undesired currents picked up by theantenna may be opposed by undesired currents picked up by the line. 1

Another object is to provide an improved means for balancing a transmission line between a receiving antenna and receiving apparatus whereby the balance will be substantially independent of frequency.

.A further object is to provide improved and simplified means for balancing atransmission line. and a shielded balanced transformer'forcoup1ing the line and associated radio receiver.

My invention may be best understood by reference to the accompanying drawing in which-'- by Fig. 1 is a schematic circuit diagram of one embodiment of myinvention, and

Fig. 2 represents a modification of the antenna system of Fig. 1. a i

40: In Fig.1 an antenna is connected to a transformer 3,.which is resonant within the high frequency'band, as follows: The primary 5 is connected to the antenna Ithrough a capacitor 1 and to ground 9. The secondary of the transformer 3 is inductively coupled to the primary 5 and is comprised of a pair of windings I3 which are serially connected by a capacitor l5. The capacitor l5 is connected to the conductors l1, 19 of a transmission line 2|. 7 The transmis- 5 sion line may be of the transposed or shielded A transformer 23, resonant within the low frequency band,is connected as follows: The primary 25 is connected between the antenna and ground. The secondary is inductively coupled to the primary 25 and is comprisedof a pair of windingsll, 29, which are serially connected together by a capacitor 3|. The secondary circuit 21', 29, 3| is-connected to the terminals of the capacitor l5. A capacity shield 33 is interposed 5 between theprimary and. secondary circuits of both transformers 3, 23 which maybe mounted in a shielded container 35. At points 31, 39, preferably near the termination of the transmission line, are connected the. terminals of an ad- .1 justable potentiometer 4| The slider 43 of the potentiometer is grounded.

. Some'capacity unbalance, represented by C, will generally exist, or may be purposely introduced, between one of the conductors l1 and 15 ground with respect to the other conductor l9 and ground. The conductor l9 which has the lower value of capacity is supplemented by a variable capacitor 45 which is connected between the conductor l9 and-ground. The terminals of go the transmission line 2| are connected to a balanced' network. a The network may be comprised of symmetrically arranged primaries 41, 49 which are'serially connected by a fixed capacitor 5|. A second pair of balanced primaries 53; 55, which 5 V are serially connected by a capacitor 51, are connected across the fixed capacitor 5|.

The balanced primaries 41, 49 and 53, 55 are respectively inductively coupled to a pair of secondaries 59, 6|. primaries and secondaries is eliminated by an appropriate shield 63. ;In' certain transformers,

I have found it possible to use the shielding action of thegrounded end of one of the secondaries in place of the physical shield. The secondary wind- 35 ings 59, 6| are grounded. One of the windings 59 is coupled through a capacitor 65 to the antenna post of a radio receiver 61 or other utilization circuit. The other secondary BI is connected directly to the antenna post of the receiver. The 4 transformer is preferably included in a grounded shielded container 69.

In this embodiment, as well as the antenna transformers 3, 23 previously described, the upper balanced primary circuit 41, 49, 5! is resonant 45 within the high frequency band, while the lower primary circuit 53, 55, 51 is resonant within the low frequency band. At low frequencies the reactance of primary coils 41, 49 is negligibly small; while the reactance of capacitor 5| is so high that it may be neglected. The secondary circuits 59, 65, 6| are broadly tuned to the same resonant frequencies as the primary circuits within their respective high and low frequency bands. The coupling between the primary and secondary Capacity coupled between the 0 circuits may approach optimum coupling depending upon the band pass characteristics required. a

It should be understood that a dipole antenna may be substituted for the grounded antenna system of Fig. 1. In Fig. 2 a dipole antenna H, 13 is represented as being connected to the transmission line 15 through transformers. I1, 19, which are essentially the same as the antenna. transformers 3, 23 of Fig. 1. The remainder of the connections from the transmission line [5 to the receiver are the same as previously described. In either system it should be understood that the transformers are arranged With suitable terminating impedance in accordance with well known practice. Likewise, single transformers are used for a system which is only used throughout a single band of frequencies.

The operation of the system is essentially as, follows: The receiver or utilization circuit is operated in the normal manner. If undesired noise impulses are received, the slider 43 of potentiometer 4| and the variable capacitor 45 are adjusted until the noise is eliminated or minimized. It

should be understood that noise impulses induceddirectly in the antenna, or picked up directly by the receiver cannot always be eliminated by balancing the transmission line. However, I have found it possible to eliminate noise impulses, from a a single source, which are picked upchiefly by the transmission line or which come in on the power supply wires. By way of example, a potentiometer having a resistance of the order of 10,000 ohms, and a variable capacitor of -100 micromi- .crofarads have proven satisfactory. Although maximum elimination of noise impulses is affected by adjustment of the balancing network M, 45 for each frequency, I have found that a substantial degree of minimization of noises is independent of frequency, once the balance is made.

Thus,'I have described an antenna system, a transmission line, including balancing means, and a balanced transformer for terminating the line. The line is balanced by an appropriate adjustment to minimize or eliminate the directly induced noise impulses. While I have illustrated one type of shielded balanced terminating transformer, it should be understood that any suitable type of transformer may be employed. The entire system, excepting the antenna per se, is arranged to eliminate direct pick-up.

I claim as my invention:

1. An antenna system comprising an antenna, a transmission line, means for transferring currents from said antenna to said line, means for balancing the conductors of said line with respect to ground, said means comprising a potentiometer having a resistance substantially higher than the impedance of said line and a variable capacitor connected between one side of said line and ground, a utilization circuit, and a balanced network for coupling said line and said utilization circuit.

2. An antenna system comprising an antenna, a transposed transmission line, means for transferring currents from said antenna to said line, means for minimizing direct pick-up by said transmission line comprising a potentiometer connected across said line and having its adjustable contact grounded, and a variable capacitor connected from one conductor of said line to ground, a utilization circuit, and means for coupling said line and said utilization circuit.

3. An antenna system comprising an antenna, a transposed transmission line, means for coupling said line and said antenna, means for minimizing direct pick-up by said transmission line comprising a potentiometer having a resistance of the order of ten thousand ohms connected across said line and having its adjustable contact grounded, and a variable capacitor connected from one conductor of said line to ground, a utilization circuit, and means for coupling said line and said utilization circuit.

4. An antenna system comprising an antenna, a transmission line, means for effectively con-- necting said antenna and said line, means for minimizing direct pick-up by said transmission line comprising a potentiometer connected across said line and a capacitor connected between one sideo-i said line and ground, a radio receiver and means coupling said line and said receiver comprising pairs of balanced primaries, a pair of secondaries and means respectively inductively coupling said pairs of primaries and said secondaries.

5. An antenna system comprising an antenna, a transposed transmission line, means for transferring currents from said antenna to saidline, means for -minimizi-ng direct pick-up by said transmission line comprising a potentiometer connected across said line and having its adjustable contact grounded, and a variable capacitor connected from one conductor of said line to ground, a utilization circuit, and means for coupling said line and said utilization circuit, comprising pairs ofbalanced primaries, a pair of secondaries, means respectively inductively coupling said pairs of primaries and said secondaries, and means for eliminating capacity coupling between said primaries and secondaries.

6. An antenna system comprising an antenna. a transmission line, means for transferring currents from said antenna to said line, means for balancing the conductors of said line with respect to ground, said means comprising a potentiometer having a resistance substantially higher than the impedance of said line and a variable capacitor, a utilization circuit, a balanced network for coupling said line and said utilization circuit, said balanced network comprising a pair of primaries serially coupled by a capacitor, a second pair of primaries serially coupled by a second capacitor and connected across said first-mentioned capacitor, and secondaries respectively coupled to said pairs of primaries.

VERNON D. LANDON. 

